Human sperm cells are seen attempting to swim right to left through an artificial stricture in this experiment headed by Alireza Abbaspourrad of Cornell University in New York. Photo: Alireza Abbaspourrad

Human sperm cells are seen attempting to swim right to left through an artificial stricture in this experiment headed by Alireza Abbaspourrad of Cornell University in New York. Photo: Alireza Abbaspourrad